Correct way to retrieve token for FCM - iOS 10 Swift 3

Question

i had implement Firebase with FirebaseAuth/FCM etc and did sent notification successfully through Firebase Console.

However i would need to push the notification from my own app server.

i am wondering below which way is correct way to retrieve the registration id for the device:-

1) retrieve registration id token from didRegisterForRemoteNotificationWithDeviceToken

func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
    var token = ""

    for i in 0..<deviceToken.count {
        token += String(format: "%02.2hhx", arguments: [deviceToken[i]])
    }

    print("Registration succeeded!")
    print("Token: ", token)
    Callquery(token)

}

2) Retrieve Registration token from firebase (Based on Firebase document which retrieve the current registration token)

let token = FIRInstanceID.instanceID().token()!

i was using the first way, the push notification is not being received even the registration id is stored on my app server database accordingly and i get this CURL session result :-

{"multicast_id":6074293608087656831,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"InvalidRegistration"}]}

i had also tried the second way and get fatal error while running the app as below:-

appreciated if anyone could point me the right way, thanks!

Answer 1

The tokenRefreshNotification function doesn't always get called when launching the app.

However, when placing the code inside the regular didRegisterForRemoteNotificationsWithDeviceToken delegate function, I can get the token every time:

func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
    if let refreshedToken = InstanceID.instanceID().token() {
        print("InstanceID token: \(refreshedToken)")
    }
}

(Swift 3 + Firebase 4.0.4)